The aeration of waste liquid media, including for example domestic sewage and industrial waste waters, is an old art. The activated sludge process, which includes aeration of liquors containing domestic sewage, has been in continuous use for about sixty years.
The liquid media treated in such aeration processes very commonly contain organic and/or inorganic foulants such as for example relatively insoluble salts which are responsible for the hardness of the water, and living and non-living organic residues which contribute to the formation of scales and slimes. Upon aeration of these media with submerged aeration devices, there is a tendency for the foulants to progressively foul such devices at the point of release of oxygen-containing gas into the liquid media, closing up or otherwise modifying the openings through which the oxygen-containing gas is released into the media with various undesirable results.
Such fouling can impair the uniformity of gas distribution from aeration devices, especially when such devices are of the area discharge type, such as for example the flat porous ceramic plates which were used to discharge air into sewage liquors in early activated sludge plants. Also, fouling can in certain circumstances increase the pressure differential required to drive oxygen-containing gas through the aeration devices at a given flow rate, thus either reducing the flow of oxygen available, and therefore the oxygen transfer rate of the aeration system, and/or increasing the amount of power consumed in maintaining the desired rate of flow, thus substantially increasing the energy requirements and cost of the process.
Since these fouling phenomena are often progressive in nature they can eventually lead to a complete or near complete disablement of the aerating devices if permitted to continue long enough. Accordingly, it is a goal of the present invention to provide methods and apparatuses for effectively monitoring the status of the aeration devices while in operation, and particularly, the dynamic wet pressure of operating aeration devices.